Silicone coated abrasion resistant polycarbonate article

ABSTRACT

A non-opaque coated polycarbonate shaped article, and a process for producing the same, having improved abrasion and chemical solvent resistance comprising a polycarbonate substrate having thereon (i) a primer layer comprised of a thermoplastic acrylic polymer containing functional groups; and (ii) a top coat containing a thermoset organopolysiloxane on said primer layer. The process for producing said coated polycarbonate article comprises the steps of: (i) priming the surface of a polycarbonate substrate by forming a primer layer comprised of a thermoplastic acrylic polymer containing functional groups; (ii) applying a top coat composition containing a further curable organopolysiloxane onto the primed substrate; and (iii) curing the further curable organopolysiloxane to form a hard, abrasion and chemical solvent resistant top coat which is tenaciously and durably adhered to the polycarbonate substrate.

This invention relates to non-opaque abrasion and chemical solventresistant organopolysiloxane coated shaped polycarbonate articleswherein the organopolysiloxane top coat is uniformly and tenaciouslyadhered to the polycarbonate substrate, and to a process for producingsuch an article. More particularly, the present invention relates to anorganopolysiloxane coated polycarbonate article having a primer layerdisposed between the polycarbonate substrate and the organopolysiloxanetop coat comprising a thermoplastic acrylic polymer containingfunctional groups. The process for producing said article comprisespriming the polycarbonate substrate with an adhesion promotingtheromplastic acrylic polymer containing functional groups by forming afilm of said acrylic polymer on the surface of the polycarbonatearticle; applying onto the primed surface a further-curableorganopolysiloxane top coat composition; and curing the further-curableorganopolysiloxane to form a uniform and tenaciously adherent abrasionand chemical resistant top coat.

BACKGROUND OF THE INVENTION

The use of transparent glazing materials utilizing polycarbonate resinas a structural component for windows, windshields and the like are wellknown. While these polycarbonate resins are easily fabricated into thedesired shape and have excellent physical and chemical properties, suchas being less dense than glass and having more breakage resistance thanglass, their abrasion and chemical solvent resistance is relatively low.

In order to overcome this relatively low abrasion resistance and tootherwise improve the surface characteristics of the polycarbonatesubstrate, various coatings have been applied to the polycarbonateresins. U.S. Pat. No. 3,582,398 describes a fabricated polycarbonatepart having improved optical properties consisting of a polycarbonatesubstrate having a transparent coating thereon consisting of athermoplastic polymethylmethacrylate. U.S. Pat. No. 4,061,652 describesa coating for polycarbonate resins comprised of (i) an acrylic resinwhich is a mixture of olefinically unsaturated organic monomers incombination with an acrylic polymer, and (ii) certain urethanes ofhydroxybenzotriazoles and hydroxybenzophenones in combination withcertain catalysts. U.S. Pat. Nos. 3,451,838, 3,986,997 and 4,027,073disclose organopolysiloxane coating compositions and techniques for theapplication of these organopolysiloxane coatings onto polycarbonatesurfaces. While these coatings have many desirable properties, e.g.,they are hard, abrasion resistant, and chemical solvent resistant, theseorganopolysiloxane coatings do not in all instances possess therequisite degree of uniform adherence to and durability on thesepolycarbonate surfaces. U.S. Pat. No. 3,707,397 describes a process forproviding a hard coating on, inter alia, polycarbonate articles, saidprocess including priming the polycarbonate surface with an adhesionpromoting thermosettable acrylic and applying an organopolysiloxane ontothe primed surface. An article produced by this process, whilepossessing acceptable initial adherence of the organopolysiloxane to thesubstrate, suffers from the disadvantage that upon prolonged exposure toweathering, and particularly to sunlight, the organopolysiloxanegenerally tends to lose its initial adherence to the substrate.Furthermore, as the thickness of the thermoset acrylic primer layerincreases, the abrasion resistance of the coated article generallydecreases. There thus remains a need for non-opaque polycarbonatearticles having uniformly, tenaciously and durably adhered abrasion andchemical resistant coatings thereon, and it is a primary object of thepresent invention to provide such articles and a relatively simple andeconomical process for producing these articles.

DESCRIPTION OF THE INVENTION

This invention relates to non-opaque organopolysiloxane coatedpolycarbonate articles having a thermoplastic functional groupcontaining acrylic polymer, adhesion promoting primer layer disposedbetween the polycarbonate surface and the organopolysiloxane, and to aprocess for producing these articles.

In the practice of the present invention, prior to the application ofthe organopolysiloxane coating to the polycarbonate surface, the surfaceis first primed by the application thereon of a primer layer containinga thermoplastic acrylic polymer having functional groups.

The aromatic carbonate polymer of the instant invention has recurringunits of the formula: ##STR1## wherein each --R-- is selected from thegroup consisting of phenylene, halo-substituted phenylene and alkylsubstituted phenylene; and A and B are each selected from the groupconsisting of hydrogen, hydrocarbon radicals free from aliphaticunsaturation and of radicals which together with the adjoining ##STR2##atom form a cycloalkane radical, the total number of carbon atoms in Aand B being up to 12.

The aromatic carbonate polymer of this invention may be prepared bymethods well known in the art and as described in U.S. Pat. No.3,989,672 all of which are incorporated by reference.

Also, included herein are branched polycarbonates wherein apolyfunctional aromatic compound is reacted with the dihydric phenol andcarbonate precursor to provide a thermoplastic randomly branchedpolycarbonate wherein the recurring units of formula I. containbranching groups.

The preferred polycarbonate resins may be derived from the reaction ofbisphenol-A and phosgene. These polycarbonates have from 10-400recurring units of the formula: ##STR3##

The polycarbonate should have an intrinsic viscosity between 0.3 and1.0, preferably from 0.40 to 0.65 as measured at 25° C. in methylenechloride.

The term "theromplastic acrylic polymer having functional groups" asused herein is meant to embrace within its scope those thermoplasticpolymers resulting from the polymerization of at least one substitutedacrylic or methacrylic ester monomer represented by the general formula

    CH.sub.2 ═CY-COOR.sup.1 X                              III.

wherein Y is hydrogen or a methyl radical; R¹ is an alkyl group,preferably an alkyl group containing from 1 to about 20 carbon atoms;and X is a hydroxyl, carboxyl, amine, epoxide, amide, SH, SO₃ H, COOR²and Si(OR³)₃ group, wherein R² and R³ are alkyl groups, preferably alkylgroups containing from 1 to about 20 carbon atoms. Copolymers resultingfrom the polymerization of two or more of substituted acrylic ester andsubstituted methacrylic ester monomers are also included within the termthermoplastic acrylic polymer having functional groups as it appearsherein. Also included within the term thermoplastic acrylic polymerscontaining functional groups as used herein are copolymers resultingfrom the copolymerization of acrylic acid esters, i.e., acrylate,monomers and/or methacrylic acid esters, i.e., methacrylate, monomerswith the aforedescribed substituted acrylic ester or substitutedmethacrylic ester monomers. Exemplary acrylate and methacrylate monomerswhich can be copolymerized with the substituted acrylic ester and/orsubstituted methacrylic ester monomers to form the thermoplastic acrylicpolymers containing functional groups include methyl acrylate, ethylacrylate, butyl acrylate, 2-ethylhexylacrylate, methyl methacrylate,ethyl methacrylate, butyl methacrylate, hexyl methacrylate, etc.Examples of copolymers of this type include copolymers containing ethylmethacrylate and hydroxyethyl methacrylate, ethyl methacrylate andγ-methacryloxy-propyltrimethoxysilane, methyl acrylate and hydroxyethylacrylate, and the like. The polymerization of the above monomericsubstituted acrylates and methacrylates to provide the thermoplasticacrylic polymer having functional groups useful in the practice of thepresent invention may be accomplished by any of the well knownpolymerization techniques.

Typical substituted acrylic and methacrylic acid ester monomersrepresented by formula III are set forth in Table I.

                  TABLE I                                                         ______________________________________                                        CH.sub.2C(CH.sub.3)COOCH.sub.2 CH.sub.2 OH                                    CH.sub.2CHCOOCH.sub.2 CH.sub.2 OH                                             CH.sub.2CHCOOCH.sub.2 CHOHCH.sub.3                                            CH.sub.2CHCOOCH.sub.2 CHNH.sub.2 CH.sub.3                                     CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 NH.sub.2                      CH.sub.2CHCOOCH.sub.2 CH.sub.2 NH.sub.2                                       CH.sub.2CHCOOCH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3                            CH.sub.2 CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3          CH.sub.2CHCOOCH.sub.2 CH.sub.2 COOH                                           CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 CH.sub.2 COOH                 CH.sub.2CCH.sub.3 COO(CH.sub.2).sub.6 SH                                       ##STR4##                                                                     CH.sub.2CH COO CH.sub.2 CH.sub.2 CH.sub.2 CONH.sub.2                           ##STR5##                                                                     CH.sub.2CCH.sub.3 COOCH.sub.2 CH.sub.2 CH.sub.2 COOCH.sub.2 CH.sub.3           ##STR6##                                                                      ##STR7##                                                                     ______________________________________                                    

The term thermoplastic acrylic polymers containing functional groups asused herein thus includes homopolymers obtained from the polymerizationof substituted acrylic ester monomers and substituted methacrylic estermonomers, copolymers obtained from the polymerization of two or moresubstituted acrylic ester monomers, copolymers obtained from thepolymerization of two or more substituted methacrylic ester monomers,copolymers obtained from the polymerization of at least one substitutedacrylic ester monomer with at least one substituted methacrylic estermonomer, and copolymers obtained from the polymerization of at least onesubstituted methacrylic ester and/or substituted acrylic ester monomerwith at least one acrylic ester and/or methacrylic ester monomer.

Mixtures of two or more of the aforedescribed homopolymers or copolymerscan also be used in the practice of the present invention.

For acceptable results, the thermoplastic acrylic polymers containingfunctional groups should have a molecular weight of at least 20,000 andpreferably at least 50,000.

The thermoplastic acrylic polymers containing functional groups of theinstant invention differ from thermosettable acrylic polymers in thatthese thermoplastic polymers are formed and applied as primers underconditions such that these functional groups do not react betweenthemselves to effect a cross-linkage between the polymer chains. Thus,the primer layer contains thermoplastic acrylic polymers containingfunctional groups.

The thermoplastic acrylic polymers containing functional groups are ingeneral applied as primers from a primer composition containing saidthermoplastic acrylic polymers and a volatile solvent, either organic orinorganic in nature, which is generally substantially inert, i.e., willnot greatly affect the polycarbonate part to be treated, but which iscapable of dissolving the thermoplastic acrylic polymers. Generally, theconcentrations of the thermoplastic acrylic polymer in the primingcomposition ranges from about 0.5 to about 25 percent by weight,preferably from about 1 to about 15 percent. Examples of suitablesolvents include ethylene glycol diacetate, butoxyethanol,methylene-dichloride, 1,2-dichloroethylene, chloroform, benzene, tolueneand the like.

The primer compositions of the instant invention may also optionallycontain various flatting agents, ultraviolet light absorbent agents,surface active agents and thixotropic agents. All of these additives andthe use thereof are well known in the art and do not require extensivediscussions. Therefore, only a limited number will be referred to, itbeing understood that any compounds possessing the ability to functionin such a manner, i.e., as a flatting agent, surface active agent, andultraviolet light absorbent agents can be used.

The various surface-active agents, including anionic, cationic andnonionic surface-active agents are described in Kirk-Othmer Encyclopediaof Chemical Technology, Vol. 19, Interscience Publishers, New York,1969, pp. 507-593, and Encyclopedia of Polymer Science and Technology,Vol. 13, Interscience Publishers, New York, 1960, pp. 477-486, both ofwhich are references and incorporated herein.

Exemplary ultraviolet light absorbent compounds or stabilizers includethose of the hydroxy benzophenone or benzotriazole series. Examples ofthese are: 2-hydroxy-4-n-octoxybenzophenone, substitutedhydroxyphenylbenzotriazole,2-(2'-hydroxy-5'-methylphenyl)-benzotriazole, and2-hydroxy-4-methoxybenzophenone. Further examples of ultraviolet lightabsorbers which may be used in the practice of this invention may befound in U.S. Pat. No. 3,043,709. In general, the amount of theultraviolet light absorber may vary from about 0.5 to about 15 percentby weight based upon the weight of the priming composition.

A uniform film of the primer composition is applied onto thepolycarbonate surface by any of the known means, such as dipping,spraying, roll-coating and the like. After the formed polycarbonate partis coated with the primer composition, the inert volatile solvent may beremoved by drying the coated article until the volatile solventevaporates, leaving a primer layer or coating containing thethermoplastic acrylic polymer containing functional groups on thepolycarbonate surface to which the primer composition was applied. Thedrying operation may be hastened by the use of drying apparatus such as,for example, a drying oven. Generally, the primer layer is a uniformfilm having a thickness varying between about 0.002 mil to about 1 mil,preferably between about 0.01 mil to about 0.5 mil.

After the polycarbonate article which is to be coated has been primed bythe application thereon of the primer composition and the evaporation ofthe solvent component of the primer composition, the primed surface ofthe polycarbonate article is then coated with the organopolysiloxanecoating. In the practice of this invention, an organopolysiloxanecoating composition containing a further curable organopolysiloxane isapplied onto the solid primer and is then cured to form a thermosetorganopolysiloxane coating.

The further-curable organopolysiloxane used in the practice of theinstant invention is the partial hydrolysis and condensation product ofat least one compound represented by the general formula

    R.sup.2.sub.n SiZ(.sub.4-n)                                IV.

wherein R² represents a monovalent hydrocarbon radical and a halogenatedmonovalent hydrocarbon radical, Z represents a hydrolyzable group and nmay vary between 0 and 2. More specifically, Z is independently a membersuch a halogen, alkoxy, acyloxy and aryloxy.

Preferably, R² represents an alkyl radical containing from 1 to about 8carbon atoms such as methyl, ethyl, and propyl through octyl (bothnormal and isomeric), an alkenyl radical containing from 2 to about 8carbon atoms, such as vinyl and the normal and isomeric forms ofpropenyl through octenyl, and the phenyl radical; Z preferablyrepresents an alkoxy radical containing from 1 to about 8 carbon atomssuch as methoxy, ethoxy, propoxy, heptoxy, octoxy and the like, anacyloxy radical containing from 2 to about 9 carbon atoms such asacetoxy, propionoxy, butyroxy, pentanoxy, hexanoxy, and the like, and aphenoxy radical; and n varies from 0 to 2.

Preferred compounds of formula IV. are silanes of the formula

    R.sub.a.sup.3 Si(OR.sup.4).sub.4-a                         V.

and silanes of the formula

    R.sub.b.sup.5 Si(OCOR.sup.6).sub.4-b                       VI.

wherein R³ and R⁵ represent a monovalent hydrocarbon radical and ahalogenated monovalent hydrocarbon radical, preferably an alkyl radicalcontaining from 1 to about 8 carbon atoms, an alkenyl radical containingfrom 2 to about 8 carbon atoms, and the phenyl radical; R⁴ and R⁶represent monovalent hydrocarbon radicals and halogenated monovalentradicals such as alkyl radicals and phenyl radicals, but are preferablyalkyl radicals of 1 to 8 carbon atoms; a is 0 or 1; and b varies from 0to 2.

Upon hydrolysis, the compounds of formula IV, and more specificallythose of formulas V and VI, are converted to the corresponding silanols.Upon generation of the silanol, there is condensation of the hydroxylsubstituents to form --Si--O--Si-- bonding. The condensation is notcomplete, but rather the organopolysiloxane retains a quantity ofsilicon-bonded hydroxyl group. This partial condensate can becharacterized as a further-curable, i.e., further condensable, siloxanolpolymer. During curing of the further-curable organopolysiloxane whichhas been deposited on the primed polycarbonate substrate, these residualhydroxyls condensate to give a silsequioxane, R⁷ SiO_(3/2), wherein R⁷represents R², R³ or R⁵ above.

The further-curable organopolysiloxane may be formulated into thetop-coat composition as a solution of the further-condensable siloxanolpolymer in water and alcohol by-product as a concentrated solution offurther-condensable siloxanol in water and alcohol by-product formed byevaporating off a substantial quantity of the alcohol by-product andwater, or it may be formulated onto the top-coat composition as a solidpartially pre-cured product by evaporating off a substantial amount ofalcohol by-product and water and then partially precuring andsolidifying the concentrated product.

Examples of good silicone top coats are the foregoing alkoxy and aryloxyfunctional silanes represented by formula V. and acyloxy functionalsilanes represented by formula VI. Such alkoxy functional, aryloxyfunctional, and acyloxy functional silanes are well known materials tosilicone manufacturers and are easily obtainable.

With respect to the acyloxy functional silanes, these materials aregenerally applied without any solvent since it has been found that theuse of solvents in the application of such top coats at times seriouslydegrades the applied silicone top coat. Preferably, the silanes ofFormula VI, that is the acyloxy functional silanes, are applied at 100%solids or from 20 to 100% solids, in the case of the acyloxy silaneswhere the solids are less than 100% the silane is simply the waterhydrolysis and partial condensation product of the foregoing acyloxyfunctional silanes of Formula VI. The alkoxy and acyloxy functionalsilanes of Formula V are generally applied from a top-coat compositioncontaining solvents in a solids concentration of from about 20 to 95% byweight. Examples of solvents which may be used in the formulation of thetop-coat composition include methanol, ethanol, butanol, ethyl acetate,benzene, toluene, xylene, ethylene glycol and the like. However, thealkoxy and aryloxy functional silanes may also, similarly to the acyloxyfunctional silanes, be applied from a top-coat composition whichcontains no solvents other than the alcohol by-product and water used toform the partial hydrolysis and condensation products of these silanes.

With respect to the foregoing aryloxy functional, alkoxy functional andacyloxy functional silanes mentioned above, such materials are wellknown in the art as, for instance, in U.S. Pat. Nos. 3,888,815 and3,701,753, both of which are incorporated herein by reference.

One particular class of further-curable organopolysiloxanes which areemployed in the top-coat compositions of the present invention are thepartial hydrolysis and condensation products of alkoxy functionalsilanes, preferably alkyltrialkoxysilanes, preferably thosealkyltrialkoxysilanes wherein the alkyl group contains from 1 to about 8carbon atoms, and aryltrialkoxysilanes, preferablyphenyltrialkoxysilanes, or mixtures thereof, wherein the alkoxy groupcontains from 1 to about 8 carbon atoms, such as, for example, methoxy,ethoxy, isopropoxy, butoxy, pentoxy, hexoxy, octoxy, and the like. Thefurther-curable organopolysiloxanes are generally prepared by a processwherein the alkyltrialkoxysilane, aryltrialkoxysilane, or a mixture ofalkyltrialkoxysilane and aryltrialkoxysilane is heated in the presenceof water, wherein the molar ratio of water to total silane is at leastabout 1.5:1 and in the presence of an effective amount of a hydrolysiscatalyst, such as a mineral acid, for example, HCl, for about 1 to about10 hours at a temperature between ambient and reflux to produce asiloxane partial condensation product; the partial condensation productis then concentrated by heating to remove 50 to about 90 mole percentalkanol by-product and some water, and thereafter, the concentratedpartial condensation product is precured by heating at a temperaturebelow the gel point thereof and generally in the range of about 70° to300° C. to produce the solvent-soluble, further curableorganopolysiloxane. This precured solvent-soluble, further-curableorganopolysiloxane is then dissolved in a suitable solvent to form thetop-coat composition and the primed polycarbonate substrate is thencoated with this top coat composition. The solvent is then evaporatedand the residual further-curable organopolysiloxane is cured to athermoset state to provide a uniformly and tenaciously adhered top coaton the primed polycarbonate substrate. The curing is effected atelevated temperatures in the range of about 50° to 135° C. for timesbetween about 1 hour to about 72 hours, depending on the temperature atwhich the cure is effected. The silicone top coat generally should becured preferably at an elevated temperature to effect the proper cure,but the temperature should be below the glass transition temperature ofthe polycarbonate. Of course, if the glass transition temperature of thepolycarbonate is exceeded, then the polycarbonate part may becomedeformed and lose its utility.

One particular further curable organopolysiloxane that can be employedin the top coat composition of the instant invention is the partialhydrolysis and condensation product of methyltriethoxysilane. Thisfurther-curable organopolysiloxane is prepared by hydrolyzingmethyltriethoxysilane with water in the presence of an effective amountof a hydrolysis catalyst, such as HCl, for about 1 to 10 hours at atemperature generally between 40° C. and reflux temperature, to producea partial condensation product. This partial condensation product isthen concentrated by heating to remove some of the alkanol by-productand water. This concentrated product is then partially pre-cured at atemperature of about 70° to about 300° C. and below the gel pointthereof and then solidified to provide a solid, solvent-soluble, furthercurable organopolysiloxane. The solid, solvent-soluble, further-curableorganopolysiloxane is then dissolved to a desired concentration in asuitable solvent to form the top coat composition. The top coatcomposition is then applied to the primed polycarbonate substrate, afterwhich the solvent is evaporated and the further-curableorganopolysiloxane finally cured to provide a hard, abrasion andchemical solvent resistant, thermoset organopolysiloxane top coat in thepolycarbonate substrate.

Another further-curable organopolysiloxane which may be employed in thepractice of the present invention is the partial hydrolysis andcondensation product of a mixture of methyltriethoxysilane andphenyltriethoxysilane. This organpolysiloxane is prepared by hydrolyzinga mixture of methyltriethoxysilane and phenyltriethoxysilane with waterin the presence of a hydrolysis catalyst such as HCl to produce apartial condensation product. This partial condensation product is thenconcentrated by heating to remove a substantial amount of the alkanolby-product and some water. This concentrated product is then partiallypre-cured by heating and then solidified to provide a solid,solvent-soluble, further-curable organopolysiloxane. The solid,solvent-soluble, further-curable organopolysiloxane is then dissolved toa desired concentration in a suitable solvent to form the top-coatcomposition containing a further-curable organopolysiloxane. Thetop-coat composition is then applied to the primed polycarbonatesubstrate, after which the solvent is evaporated and the further-curableorganopolysiloxane is finally cured to provide a tenaciously and durablyadhered, abrasion and chemical resistant thermoset organopolysiloxanetop coat on the polycarbonate substrate.

These are not the only silicones that may be utilized in the top-coatsof the instant invention. Less preferred silicones which can be utilizedto form the top coats of the present invention are, for instance,silicone resins composed of trifunctional and difunctional units,silicone resins composed of trifunctional units, difunctional units andtetrafunctional units when the organo substituent groups in thetrifunctional units may be selected from hydrocarbon radicals of 1 toabout 8 carbon atoms and are preferably methyl, phenyl and vinyl; andwherein the organo substituent groups in the difunctional siloxy unitsmay be selected from hydrocarbon units of from 1 to about 8 carbonatoms, preferably alkyl radicals, vinyl radicals and phenyl radicals.Such silicone resins usually have an organic to silicon atom ratio of1:1 to 1.9:1; may have a silanol content that varies anywhere from 4 to10 weight percent and optionally may have an alkoxy content that variousfrom 2 to 4%. The preparations of such silicone resins which may beutilized as top-coats in the invention of the intant case are, forinstance, to be found in U.S. Pat. Nos. 3,375,223, 3,435,001, 3,450,672,3,790,527, 3,832,319, 3,865,766, 3,887,514 and 3,925,276.

These silicones may also contain various fillers such as, for example,glass fibers, talc and silica, preferably colloidal silica.

The top-coat compositions containing the aforedescribed silicones aresimply brushed, dipped, sprayed or flowed on top of the primer layerthat is applied to the polycarbonate substrate. The solvent, or alcoholby-product and water, present in the top-coat composition is evaporatedand the residual further-curable organopolysiloxane is cured to form athermoset organopolysiloxane top coat. Preferably, the further-curableorganopolysiloxane is cured at elevated temperatures. Although certaincatalysts may be utilized to accelerate the cure of the further-curableorganopolysiloxane, such catalysts are not necessary if thefurther-curable organopolysiloxane is cured by itself at the elevatedtemperature for a sufficient length of time.

Another embodiment of the present invention is a process of producing adurably adherent, mar, and chemical resistant silicone coating on apolycarbonate article. The process comprises the steps of: (i) applyingonto the polycarbonate substrate a primer composition containing athermoplastic acrylic polymer dissolved in a suitable solvent; (ii)evaporating of the solvent to leave a solid thermoplastic acrylicpolymer containing primer layer on the polycarbonate substrate; (iii)applying a top-coat composition containing a further-curableorganopolysiloxane onto the primed polycarbonate substrate; (iv)evaporating off the volatile solvents present in the top coatcomposition to form a residue of further-curable organopolysiloxane onthe primed polycarbonate substrate; and (v) curing the further-curableorganopolysiloxane to form a top coat containing a thermosetorganopolysiloxane.

PREFERRED EMBODIMENT OF THE INVENTION

In order that those skilled in the art may better understand how thepresent invention may be practiced, the following examples are given byway of illustration and not by way of limitation.

EXAMPLE 1

An aromatic polycarbonate is prepared by reacting2,2-bis(4-hydroxyphenyl) propane and phosgene in the presence of an acidacceptor and a molecular weight regulator and having an intrinsicviscosity of 0.57. The product is then fed to an extruder, whichextruder is operated at about 265° C. and the extrudate is comminutedinto pellets.

The pellets are then injection molded at about 315° C. into test panelsof about 4 in. by 4 in. by about 1/8 in. thick. The test panels aresubjected to an abrasion test. The abrasion test is one wherein testpanels having a 1/4 inch diameter hole cut in the center are subjectedto a Taber Abraser. The Taber Abraser is equipped with CS-10F wheelswhich are resurfaced every 200 cycles by abrading for 25 cycles on aS-11 refacing disc. The weights used in combination with the CS-10Fwheels are 500 gm. weights. Initial measurements of % Haze are made atfour places around the future wear track of the sample using a GardnerHazemeter. The sample is abraded for 300 cycles, cleaned withisopropanol, and the % Haze is remeasured at the same four places. Thefour differences in % Haze are calculated and averaged to give the Δ%Haze. The results are set forth in Table II.

EXAMPLE 2

A top-coat composition is prepared by adding to 100 parts by weight of acommercially available further-curable organpolysiloxane 2 parts byweight of a commercially available curing catalyst. This further-curableorganopolysiloxane is available from Resart-Ihm A.G., Mainze, FederalRepublic of Germany, as their Resarix SFPC.sup.(R) and is a solutioncontaining about 32 weight percent of the partial hydrolysis andcondensation product of methyl triethoxysilane dissolved and a solventsystem consisting of ethanol-tetrahydrofuran-n-butanol-ethoxyethanol.The catalyst consists of a solution containing 2 weight percent oftetraethylammonium hydroxide and a methanol solvent.

EXAMPLE 3

Primer compositions are formulated by dissolving in a solvent systemcontaining 20 parts ethyleneglycol diacetate and 80 parts butoxyethanola desired amount of a thermoplastic acrylic polymer containingfunctional groups formed by the copolymerization of a methacrylatemonomer and a functionalized methacrylate monomer. This primercomposition is flow coated on polycarbonate test panels preparedsubstantially in accordance with Example 1. Excess primer composition ispermitted to drain off and the test panels are dried for 15 minutes at125° C. to evaporate the solvent and produce a solid primer layer. Theseprimed panels are then flow coated with the further-curableorganopolysiloxane top coat composition produced substantially inaccordance with Example 1. Excess top coat composition is permitted todrain off and the test panels are air dried for 30 minutes and arethereafter subjected to 1 hour of heating at 125° C. to cure thefurther-curable organopolysiloxane. These primed, top coated test panelsare then subjected to the above described abrasion test and to anadhesion test which consists of using a multiple blade tool to cutparallel grooves about 1 mm apart through the coating into thesubstrate, rotating the sample 90° and repeating the cutting processthereby forming a grid pattern of 1 mm squares cut into the coating, andapplying an adhesive tape over the cross-hatched area and quicklypulling said tape off. (A sample fails the adhesion test if any of thesquares in the grid are pulled off.) The results of the adhesion testand abrasion test, as well as the concentration of the thermoplasticacrylic polymer containing functional groups in the primer composition,the thickness of the primer layer and the composition of the monomermixtures used in formulating the thermoplastic acrylic polymercontaining functional groups are set forth in Table II.

                  TABLE II                                                        ______________________________________                                                                  Primer                                              Composition,   %, by weight,                                                                            thick-       Δ%                               in parts by    of solids in                                                                             ness    Ad-  Haze                                   weight, of     primer     (in     he-  300                                    monomer mixture                                                                              composition                                                                              mils)   sion cycles                                 ______________________________________                                        Unprimed and                                                                  uncoated test panel                                                                          --         --      --   34                                     of Example 1                                                                  97  parts of methyl-                                                              methacrylate                                                              3   parts hydroxy- 5          0.02  Pass 5.3                                      ethyl methacrylate                                                        98  parts ethyl                                                                   methacrylate   2          0.02  Pass 5.2                                  2   parts glycidyl                                                                methacrylate                                                              49  parts methyl                                                                  methacrylate                                                              49  parts n-butyl  10         0.05  Pass 4.9                                      methacrylate                                                              2   parts hydroxyethyl                                                            methacrylate                                                              97  parts methyl                                                                  methacrylate   15         0.27  Pass 3.1                                  3   parts hydroxy-                                                                ethyl methacrylate                                                        98  parts ethyl                                                                   methacrylate   20         0.31  Pass 5.2                                  2   parts ν-methacryloxy-                                                      propyltrimethoxy-                                                             silane                                                                    ______________________________________                                    

EXAMPLE 4

This example is designed to illustrate the criticality of the particularcombination of the thermoplastic acrylic polymer primer layer containingfunctional groups and organopolysiloxane top coat in providing a durableand tenaciously adhered coating effective to produce an abrasionresistant polycarbonate article. Unprimed polycarbonate panels areprepared substantially in accordance with Example 1 and are flow-coatedwith the Resarix SF/PC.sup.(R) organopolysiloxane top coat compositionprepared substantially in accordance with Example 2. Excess top coatcomposition is permitted to drain off and the coated unprimed testpanels are air dried for 30 minutes to evaporate the solvent, followedby a one-hour bake at 250° F. to cure the further-curableorganopolysiloxane. These unprimed coated test panels are subjected tothe aforedescribed adhesion and abrasion tests and the results are setforth in Table wII.

                  TABLE III                                                       ______________________________________                                        Sample     Adhesion    Δ% Haze, 300 cycles                              ______________________________________                                        Example 4  Failed      10.3                                                   ______________________________________                                    

As can be seen from Tables II and III, the adhesion of theorgonopolysiloxane top coat to the umprimed polycarbonate panels ismarkedly inferior. As a matter of fact, it is unsatisfactory, ascompared to the adhesion of the organopolysiloxane top coat to thepolycarbonate panels primed in accordance with the present invention.

EXAMPLE 5

This example is likewise designed to illustrate the criticality of theparticular combination of the thermoplastic acrylic polymer primer layercontaining functional groups and organopolysiloxane top coat of theinstant invention in providing a durable and tenaciously adhered coatingeffective to produce an abrasion resistant polycarbonate article.EV-6174, a commercially available thermosettable acrylic (32% solids inbutanol) available from Bee Chemical Company, is diluted with n-butanolto various solids concentrations. Into these solutions are dippedpolycarbonate test panels prepared substantially in accordance withExample 1. The polycarbonate panels are then removed from the primingsolutions and are allowed to remain in the open air for about 30minutes, during which time the solvent from the priming solutionsevaporates and deposits a thin priming film on the polycarbonatesurface. The primed test panels are then flow coated with anorganopolysiloxane top coat composition prepared substantially inaccordance with Example 2. Excess top coat composition is permitted todrain off and the test panels are air dried for 30 minutes and arethereafter subjected to 1 hour of heating at 125° C. These primed andtop coated test panels are subjected to the aforedescribed adhesion testand to the abrasion test. The results of these tests, as well as theconcentration of the thermosettable acrylic in the primer solution andthe thickness of the primer layer are set forth in Table IV.

                  TABLE IV                                                        ______________________________________                                        % Solids (thermosettable                                                                      Primer                                                        acrylic polymer) in                                                                           thickness                                                     n-butanol solution                                                                            (mils)   Adhesion  Δ% Haze                              ______________________________________                                         2              0.01     Pass      7.1                                        20              0.36     Marginal* 7.5                                        ______________________________________                                         *The results of the adhesion test were uneven. That is to say, some           samples failed the adhesion test, while other samples passed the adhesion     test.                                                                    

A comparison of Tables II and IV shows that with a thermosettableacrylic primer the abrasion resistance of the top coat, as well as theadhesion of the top coat, deteriorates as the thickness of the primerlayer increases. This is not the case with the thermoplastic acrylicprimers of the present invention, i.e., the adhesion and abrasionresistance of the top coat do not deteriorate as the thickness of theprimer layer increases.

Thus, a particular advantage of the instant thermoplastic acrylicprimers is that the abrasion resistance and adhesion of the silicone topcoat is generally not a function of primer layer thickness. It is wellknown to those skilled in the art that wedging occurs during the coatingof large polycarbonate sheets. Thus, it is a great advantage ifproperties such as abrasion resistance and adhesion are generally notdependent upon primer coating thickness.

A further advantage of having a thick primer coating is that ultravioletlight and other stabilizers can effectively be incorporated in thecoating. Polycarbonate generally undergoes photodegradation and turnsyellow during prolonged weathering. However, if the surface ofpolycarbonate can be protected from ultraviolet light, it can bestabilized against photodegradation. Incorporation of ultravioletlight-absorbers in a coating on polycarbonate is therefore highlydesirable since these materials will screen ultraviolet light fromreaching the surface of the polycarbonate. For practical purposes,however, a coating must generally be about 0.2-0.3 mils thick andcontain about 10% of an ultraviolet light-absorber before more than 90%of the incident ultraviolet light can be screened from the surface ofthe polycarbonate. Thinner primer coatings generally require much moreultraviolet light-absorbers to effectively screen more than 90% ofincident ultraviolet light. Due to the fact that the primer layers ofthe instant invention can be relatively thick, ultravioletlight-absorbers can therefore be effectively incorporated in thethermoplastic acrylic primers of the instant invention.

The foregoing disclosure of this invention is not to be considered aslimiting, since many variations may be made by those skilled in the artwithout departing from the scope or spirit of the foregoing description.For example, although the above examples are limited to only a few ofthe very many thermoplastic acrylic polymers containing functionalgroups which can be employed in the present invention, it should beunderstood that the present invention includes a much broader class ofsuch polymers as shown by formula III and the description precedingthese examples.

What we claim as new and desire to secure by Letters Patent of theUnited States is:
 1. A shaped non-opaque coated polycarbonate articlehaving improved abrasion and chemical solvent resistance comprising apolycarbonate substrate having deposited on the surface thereof (i) anadhesion promoting primer layer consisting essentially of athermoplastic substantially non-crosslinked acrylic polymer containingfunctional groups; and (ii) a tenaciously and uniformly adhered top coatconsisting of a thermoset organopolysiloxane disposed on said primerlayer.
 2. The article of claim 1 wherein said thermoplastic acrylicpolymer containing functional groups contains functional groups selectedfrom the class consisting of hydroxyl, carboxyl, amine, epoxide, amide,SH, SO₃ H, COOR, Si(OR¹)₃, or mixtures thereof, wherein R and R¹ arealkyl radicals containing from 1 to about 20 carbon atoms.
 3. Thearticle of claim 2 wherein said acrylic polymer containing functionalgroups contains the polymerization product of (i) at least one monomerrepresented by the general formula CH₂ ═CY--COOR² and at least onemonomer represented by the general formula CH₂ ═CY¹ --COOR³ X; or (ii)at least one monomer represented by the general formula CH₂ ═CY¹ --COOR²X; wherein Y and Y¹ are independently selected from hydrogen or a methylradical; R² represents an alkyl radical containing from 1 to about 20carbon atoms; R³ represents a divalent saturated aliphatic hydrocarbonradical containing from 1 to about 20 carbon atoms; and X represents ahydroxyl, carboxyl, amine, epoxide, amide, SH, SO₃ H, COOR, or Si(OR¹)₃radical wherein R and R¹ are independently selected from alkyl radicalscontaining from 1 to about 20 carbon atoms.
 4. The article of claim 3wherein said acrylic polymer contains the polymerization product of atleast one monomer represented by the general formula CH₂ ═CY--COOR³ X.5. The article of claim 3 wherein said acrylic polymer contains thepolymerization product of at least one monomer represented by thegeneral formula CH₂ ═CY--COOR³ X and at least one monomer represented bythe general formula CH₂ ═CH--COOR².
 6. The article of claim 2 whereinsaid primer layer contains an ultraviolet light absorbent compound. 7.The article of claim 1 wherein said organopolysiloxane is the hydrolysisand condensation product of at least one compound represented by thegeneral formula R_(n) ⁴ SiZ.sub.(4-n) wherein R⁴ represents a monovalenthydrocarbon radical, Z represents a hydrolyzable group, and n may varybetween 0 and
 2. 8. The article of claim 7 wherein R⁴ is selected fromthe group consisting of alkyl radicals having from 1 to about 8 carbonatoms, alkenyl radicals having from 2 to about 8 carbon atoms, and aphenyl radical.
 9. The article of claim 8 wherein Z represents an --OR⁵group wherein R⁵ is a monovalent hydrocarbon, and wherein n is 0 or 1.10. The article of claim 9 wherein R⁵ is selected from the groupconsisting of alkyl radicals containing from 1 to about 8 carbon atoms.11. The article of claim 10 wherein R⁴ is a methyl radical, R⁵ is anethyl radical, and n is
 1. 12. The article of claim 7 wherein zrepresents an --OCOR⁶ group wherein R⁶ is a monovalent hydrocarbonradical.
 13. The article of claim 7 wherein R⁴ _(n) SiZ.sub.(4-n)represents an alkyltrialkoxysilane.
 14. The article of claim 13 whereinsaid primer layer includes an ultraviolet light absorbent compound. 15.The article of claim 1 wherein said primer layer includes an ultravioletlight absorbent compound.
 16. A shaped non-opaque coated polycarbonatearticle having improved abrasion and chemical solvent resistancecomprising a polycarbonate substrate coated on at least one side thereofwith (i) an adhesion promoting primer layer consisting essentially of(a) a thermoplastic acrylic polymer containing functional groups, and(b) at least one ultraviolet light absorber; and (ii) a tenaciouslyadhered top coat consisting of a thermoset organopolysiloxane disposedon said primer layer.
 17. The article of claim 16 wherein saidfunctional groups are selected from the class consisting of hydroxyl,amine, epoxide, amide, SH, SO₃ H, COOR, Si(OR¹)₃, or mixtures thereof,wherein R and R¹ are alkyl radicals containing from 1 to about 20 carbonatoms.
 18. A shaped non-opaque coated polycarbonate article havingimproved abrasion and chemical solvent resistance comprising apolycarbonate substrate coated with (i) an adhesion promoting primerconsisting of a thermoplastic acrylic polymer having functional groups;and (ii) a top coat consisting of a thermoset organopolysiloxanedisposed on said primer.
 19. The article of claim 18 wherein saidfunctional groups are selected from hydroxyl, carboxyl, amine, epoxide,amide, SH, SO₃ H, COOR, Si(OR¹)₃, or mixtures thereof, wherein R and R¹represent alkyl radicals containing from 1 to about 20 carbon atoms. 20.A shaped non-opaque coated polycarbonate article having improvedabrasion and chemical solvent resistance comprising a polycarbonatesubstrate coated on at least one surface thereof with (i) an adhesionpromoting primer consisting of (a) a thermoplastic acrylic polymerhaving functional groups, and (b) an effective ultraviolet lightstabilizing amount of at least one ultraviolet light stabilizer; and(ii) a top coat consisting of a thermoset organopolysiloxane disposed onsaid primer.
 21. The article of claim 20 wherein said functional groupsare selected from hydroxyl, carboxyl, amine, epoxide, amide, SH, SO₃ H,COOR, Si(OR¹)₃, or mixtures thereof, wherein R and R¹ represent alkylradicals containing from 1 to about 20 carbon atoms.